首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   16718篇
  免费   439篇
  国内免费   18篇
化学   10288篇
晶体学   308篇
力学   317篇
数学   2759篇
物理学   3503篇
  2022年   280篇
  2021年   280篇
  2020年   240篇
  2019年   304篇
  2018年   313篇
  2017年   331篇
  2016年   627篇
  2015年   489篇
  2014年   612篇
  2013年   1300篇
  2012年   849篇
  2011年   969篇
  2010年   688篇
  2009年   626篇
  2008年   939篇
  2007年   812篇
  2006年   753篇
  2005年   638篇
  2004年   555篇
  2003年   475篇
  2002年   402篇
  2001年   285篇
  2000年   250篇
  1999年   190篇
  1998年   190篇
  1997年   155篇
  1996年   166篇
  1995年   190篇
  1994年   132篇
  1993年   96篇
  1992年   130篇
  1991年   122篇
  1990年   115篇
  1989年   127篇
  1988年   141篇
  1987年   111篇
  1986年   119篇
  1985年   205篇
  1984年   209篇
  1983年   142篇
  1982年   147篇
  1981年   150篇
  1980年   160篇
  1979年   118篇
  1978年   109篇
  1977年   106篇
  1976年   106篇
  1975年   91篇
  1974年   79篇
  1973年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light.  相似文献   
32.
JPC – Journal of Planar Chromatography – Modern TLC - This paper reports the efficiency of the C30 phase for HPLC and TLC separation of a mixture of tocopherol homologs and...  相似文献   
33.
A phenomenological model for describing the production of Centauro events in relativistic heavy-ion collisions is discussed. The model provides quantitative predictions for kinematical variables, for the baryon number, and for the masses of a Centauro fireball and of its decay products. A Centauro fireball decays predominantly into nucleons, strange hyperons, and possibly strangelets. Centauro events in Pb + Pb collisions at the LHC energy are simulated for the CASTOR detector. The signatures of these events are discussed in detail.  相似文献   
34.
JPC – Journal of Planar Chromatography – Modern TLC - Flavonoid glycosides are much more polar than their aglycones and the two groups of compounds are difficult to separate by planar...  相似文献   
35.
This paper presents the Galerkin approximation of the optimization problem of a system governed by non‐linear second‐order evolution equation where a non‐linear operator depends on derivative of the state of the system. The control is acting on a non‐linear equation. After giving some results on the existence of optimal control we shall prove the existence of the weak and strong condensation points of a set of solutions of the approximate optimization problems. Each of these points is a solution of the initial optimization problem. Finally we shall give a simple example using the obtained results. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
36.
37.
The disintegration of bromhexin tablets was monitored by magnetic resonance imaging. The fast imaging method FLASH with spoiling gradients was used to obtain images of the tablets in short time intervals. The rate of the disintegration depends on the preparation method, kind and percentage of the carrier (polyethylene glycol, lactose). Solid dispersion with slow evaporation of solvent yields materials with decreased dissolution rate. Increasing molecular mass of polyethylene glycol and its percentage content also hampers disintegration.  相似文献   
38.
Supported by SFB 170 “Geometrie und Analysis” at the University of G?ttingen  相似文献   
39.
The aim of this paper is to introduce the notions of floor and ceiling functions related to graph edge-decompositions intot mutually isomorphic parts. It is shown that, given any natural numbert, uniform and extremal t-packing andt-covering exist for each complete graph and each complete bipartite graph. Extremal in this context means that both a remainder and a surplus are absolutely minimum. In proofs, decompositions of multigraphs into matchings are involved. Open problems and conjectures are stated.  相似文献   
40.
Finitely generated linear semigroups over a field K that have intermediate growth are considered. New classes of such semigroups are found and a conjecture on the equivalence of the subexponential growth of a finitely generated linear semigroup S and the nonexistence of free noncommutative subsemigroups in S, or equivalently the existence of a nontrivial identity satisfied in S, is stated. This ‘growth alternative’ conjecture is proved for linear semigroups of degree 2, 3 or 4. Certain results supporting the general conjecture are obtained. As the main tool, a new combinatorial property of groups is introduced and studied.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号